1. Field of the Invention
The present invention relates to bearing apparatuses. In particular, the present invention relates to bearing apparatuses installed in motors and blower fans.
2. Description of the Related Art
Small and high-performance electronic devices, such as notebook PCs, produce a large amount of heat at CPUs and the like inside cases thereof. This makes it important to fake measures against the heat. One common measure against the heat is to install blower fans inside the cases to discharge the heat.
JP-A 11-252859, for example, discloses a heat sink apparatus arranged to be installed on an electronic device, such as a personal computer. An electric motor which uses a dynamic pressure fluid bearing is used in the heat sink apparatus. A shaft 9 which extends from a fan 8 of the heat sink apparatus is rotatably inserted in a sleeve 6. An end surface of the shaft 9 on a side opposite to the fan 8 is arranged to be a spherical surface, and is arranged to be in contact with a thruster 5 to define a thrust bearing 18. Dynamic pressure generating grooves 13 are defined in an inner circumferential surface of the sleeve 6. An oil 14 is fed into the dynamic pressure generating grooves 13 to define a radial bearing 17.
In the heat sink apparatus disclosed in JP-A 11-252859, the shaft 9 is fixed to the fan 8, and an upper end surface of the shaft 9 is exposed from an upper surface of the fan 8. Therefore, the oil may leak into a gap between the fan 8 and an upper end portion of the shaft 9 through capillary action, and then leak above the fan 6.